3. C Arrays
• An array is a variable that can store multiple values. For
example, if you want to store 100 integers, you can create an
array for it.
• int data[100];
4. How to
declare an
array?
• datatype array Name[array Size];
• For example,
• float mark[5];
• Here, we declared an array, mark, of
floating-point type. And its size is 5.
Meaning, it can hold 5 floating-point
values.
• It's important to note that the size and
type of an array cannot be changed
once it is declared.
5. Access Array
Elements
• You can access elements of an array by indices.
• Suppose you declared an array mark as above. The first
element is mark[0], the second element is mark[1] and so
on.
6. Few keynotes:
• Arrays have 0 as the first index, not 1. In this example, mark[0] is the
first element.
• If the size of an array is n, to access the last element, the n-1 index is
used. In this example, mark[4]
• Suppose the starting address of mark[0] is 2120d. Then, the address of
the mark[1] will be 2124d. Similarly, the address of mark[2] will
be 2128d and so on.
This is because the size of a float is 4 bytes.
7. How to initialize an array?
• It is possible to initialize an array during declaration. For example,
• int mark[5] = {19, 10, 8, 17, 9};
• You can also initialize an array like this.
• int mark[] = {19, 10, 8, 17, 9};
• Here, we haven't specified the size. However, the compiler knows its
size is 5 as we are initializing it with 5 elements.
8. Here,
mark[0] is equal to 19
mark[1] is equal to 10
mark[2] is equal to 8
mark[3] is equal to 17
mark[4] is equal to 9
9. Change
Value of
Array
elements
• int mark[5] = {19, 10, 8, 17, 9}
•
• // make the value of the third element
to -1
• mark[2] = -1;
•
• // make the value of the fifth element to
0
• mark[4] = 0;
10. Input and
Output
Array
Elements
• Here's how you can take input from the
user and store it in an array element.
• // take input and store it in the 3rd
element
• scan("%d", &mark[2]);
•
• // take input and store it in the ith
element
• scan("%d", &mark[i-1]);
11. Here's how you
can print an
individual
element of an
array.
• // print the first element of the array
• printf("%d", mark[0]);
•
• // print the third element of the array
• printf("%d", mark[2]);
•
• // print ith element of the array
• printf("%d", mark[i-1]);
12. Access elements out of its bound!
• Suppose you declared an array of 10 elements. Let's say,
• int testArray[10];
• You can access the array elements from test Array[0] to test Array[9].
• Now let's say if you try to access testArray[12]. The element is not
available. This may cause unexpected output (undefined behavior).
Sometimes you might get an error and some other time your program
may run correctly.
• Hence, you should never access elements of an array outside of its
bound.
13. C Multidimensio
nal Arrays
• In C programming, you can create an array of
arrays. These arrays are known as multidimensional
arrays. For example,
• float x[3][4];
• Here, x is a two-dimensional (2d) array. The array
can hold 12 elements. You can think the array as a
table with 3 rows and each row has 4 columns.
•
Similarly, you can declare a three-dimensional (3d)
array. For example,
• float y[2][4][3];
• Here, the array y can hold 24 elements.
14. Initializing a multidimensional array
Initialization of a 2d
array
• // Different ways to initialize two-
dimensional array
•
• int c[2][3] = {{1, 3, 0}, {-1, 5, 9}};
•
• int c[][3] = {{1, 3, 0}, {-1, 5, 9}};
•
• int c[2][3] = {1, 3, 0, -1, 5, 9};
Initialization of a 3d
array
• int test[2][3][4] = {
• {{3, 4, 2, 3}, {0, -3, 9, 11}, {23, 12, 23,
2}},
• {{13, 4, 56, 3}, {5, 9, 3, 5}, {3, 1, 4,
9}}};
15. Pass
arrays to a
function
in C
• Passing array elements to a function is
similar to passing variables to a
function.
• To pass multidimensional arrays to a
function, only the name of the array is
passed to the function(similar to one-
dimensional arrays).
16. Relationshi
p Between
Arrays and
Pointers
• Array in C is used to store elements of
same types whereas Pointers are
address variables which stores the
address of a variable.
Now array variable is also having a
address which can be pointed by
a pointer and array can be navigated
using pointer.
17. This Photo by Unknown author is licensed under CC BY-SA-NC.
